This invention generally relates to the transmission of data and power across a rotating interface, and more particularly, to an apparatus that can transmit both power and data across the rotating interface without requiring brushes or other contacts.
High-voltage power transformers are used in a variety of applications, such as in baggage scanner systems, computed tomography (CT) systems, wind turbines, and other electronic systems. CT systems are often used to obtain non-invasive sectional images of test objects, particularly internal images of human tissue for medical analysis and treatment. Current baggage scanner systems and CT systems position the test object, such as luggage or a patient, on a conveyor belt or table within a central aperture of a rotating frame (e.g., gantry) which is supported by a stationary frame. The rotating frame includes an x-ray source and a detector array positioned on opposite sides of the aperture, both of which rotate around the test object being imaged. At each of several angular positions along the rotational path (also referred to as “projections”), the x-ray source emits a beam that passes through the test object, is attenuated by the test object, and is received by the detector array. The x-ray source utilizes high-voltage power to generate the x-ray beams.
Each detector element in the detector array produces a separate electrical signal indicative of the attenuated x-ray beam intensity. The electrical signals from all of the detector elements are collected and processed by circuitry mounted on the rotating frame to produce a projection data set at each gantry position or projection angle. Projection data sets are obtained from different gantry angles during one revolution of the x-ray source and detector array. The projection data sets are then processed by a computer to reconstruct the projection data sets into, for example, an image of a bag or a CT image of a patient.
The circuitry mounted on the rotating frame is powered by low-voltage power, while the x-ray source is powered by high-voltage power. Conventional rotating gantry based systems utilize a brush and slip ring mechanism to transfer power at a relatively low-voltage between the stationary and rotating portions of the gantry frame. The rotating gantry portion has an inverter and high-voltage tank mounted thereon and connected to the brush and slip ring mechanism. The inverter and high-voltage tank include transformer, rectifier, and filter capacitance components that step-up the voltage from the low-voltage, transferred through the brush and slip ring mechanism, to the high-voltage needed to drive the x-ray source. The transformer in the high-voltage tank produces a high-voltage AC signal that is converted to a high-voltage DC signal by rectifier circuits inside the high-voltage tank.
Conventional rotating gantry based scanner systems have experienced certain disadvantages. The high-voltage tank and inverter on the rotating gantry portion increases the weight, volume and complexity of the system. Furthermore, the brush and slip ring mechanisms (that are typically used to carry appreciable current) are subject to reduced reliability, maintenance problems, and electrical noise generation, which interfere with sensitive electronics. As systems are developed that rotate faster, it becomes desirable to reduce the volume and weight of the rotating components.
To eliminate slip ring brushes, rotary transformers can be used to transfer power in a contactless manner to the rotating gantry. However, the voltage and current in rotating transformers used to transfer power in CT imaging systems are quite considerable. For example, a 150 KW imaging system may have a rotary transformer that operates at approximately 300 volts and 500 amperes and that generates a considerable amount of electrical noise. Extraordinary steps are required to keep this noise out of data being transmitted across the gantry. For example, some CT imaging systems utilize optical signals for data transmission. In one such system, an optical signal is injected into a mirror groove that is configured to bounce the optical signal in both directions across the gantry, from a 0 degree location to a ±180 degree location. An optical stylus is inserted into the groove from an opposite side of the gantry to pick up the optical signal. Another such system uses a plurality of optical transmitters that are multiplexed. The optical transmitters pass across a stationary shoe with an optical detector as the gantry rotates, and the optical transmitters are synchronized to the changing location of the detector. These configurations are relatively costly and complicated.
A scanner apparatus is needed that addresses the above concerns and other problems experienced in the past, and that is relatively inexpensive and simple.